OKLAHOMA CITY (CBSDFW.COM/AP) — Federal officials say Oklahoma residents with medical marijuana cards will be barred from obtaining gun permits after voters recently approved the medical use of the drug.

State residents voted in favor of the marijuana measure Tuesday. The move puts Oklahoma gun owners in a conflict 25 other states are facing between state and federal laws governing guns and marijuana.

File photo of marijuana. (credit: Uriel Sinai/Getty Images)

Federal law says it’s illegal to possess both a gun and marijuana. The conditions of a 2011 Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) open letter states that federal law prohibits anybone who is an “unlawful user of or addicted to any controlled substance” from “possessing firearms or ammunition.” And the letter says anyone who uses marijuana, regardless of state law, qualifies as an “unlawful user of” the controlled substance.

Don Spencer is the president of the Oklahoma 2nd Amendment Association. He says state gun owners who need marijuana for treatment should be allowed to possess both.

The federal Bureau of Alcohol, Tobacco, Firearms and Explosives recommends those who may consider obtaining a marijuana card to contact legal counsel or the agency for guidance on how to legally transfer, sell or dispose of firearms.

(© Copyright 2018 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)